Current Insights On The Use Of Orthotics For Limb Length Discrepancy And Morton’s Syndrome

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Identifying Structural Deficiencies In Pathomechanical Foot And Limb Function That May Contribute To Knee Disorders

Q: What is the role of pathomechanical foot and limb function in knee disorders and how can identification of inherent structural deficiencies prevent these repetitive stress problems from producing degenerative changes later in life?

A: Dr. D’Amico and Dr. Skliar concur that the increased demands of high school sports on young adolescents have resulted in an epidemic of knee injuries.

Dr. Skliar notes several such injuries in decreasing order of frequency: patella and medial knee pain, Achilles tendonitis and calf pain, shin splints and groin pain. Athletes who display greater than 6 degrees of total frontal plane varus compensations make up the largest group of those who seek professional care, points out Dr. Skliar. He says anyone with 10 degrees or higher of total varus should receive biomechanical treatment even if they are asymptomatic.

“Improper athletic shoes for the various sport activities and for different foot types can significantly aggravate or cause excessive stresses to the limbs,” notes Dr. Skliar.

Dr. Skliar suggests providing professional information concerning proper footgear for the individuals involved in a specific sport. He also says there needs to be better recognition of how the foot structure of each athlete can influence how well suited the athlete may be to a specific sport activity. As Dr. Skliar explains, feet with normally low arch structures are usually more stable due to the larger weightbearing surface they present. Those who possess a normally high arch foot are less stable in static conditions but he notes they have a mechanical advantage for speed and jumping activities. Accordingly, Dr. Skliar says a lineman of a football team would fare better with a normal low arch foot while the running back would do better with a high arch foot type.

As Dr. D’Amico says, triplanar compensation associated with any condition producing excessive pronation is not matched to the primarily sagittal plane motion at the knee joint. As a result, he notes the frontal and transverse plane demands are taking place while the foot is planted against an unyielding surface, and the superstructure is moving forward over the supporting extremity. Among other things, he says this increases medial collateral ligament stress and strain as well as the Q angle.

Schuster postulated a mechanism between pedal pronation and the production of knee pain, and recommended treating the underlying pathology via foot orthoses, according to Dr. D’Amico.1 In that article, the author goes on to say, “it is noteworthy that almost every runner we have had the opportunity to treat on a mechanical basis has had a moderate to severe forefoot varus.” Over 20 years later, Dr. D’Amico says Saxena and Haddad went on to confirm this statement in a study of 102 patients with patellofemoral pain syndrome in which they found 91 percent of patients to have had forefoot varus.2

Dr. D’Amico says the research has highly correlated malalignment of the patellofemoral mechanism with excessive pronation.3-5 He adds that an increase in the Q angle has direct correlation of knee pathology especially of mechanical origins.6

“The role of the podiatrist is to identify and neutralize structural deficiencies present in the foot, especially forefoot varus, thereby preventing dysfunction and at the same time reducing the risk of injury,” says Dr. D’Amico.

The “missing link” in all sports at any level is structural evaluation prior to training an athlete, contends Dr. Pack, who treats athletes who have $125 million contracts but have never been evaluated. As he notes, pathomechanical foot and limb function are a major cause of not just knee injuries but many other injuries. For example, Dr. Pack says for an ankle sprain, physicians readily accept the fact that a hard hit in football may be the cause but if the injured individual gets a proper evaluation, a rearfoot varus deformity, equinus of the first metatarsal or other abnormality may often be the underlying etiology.

Dr. Pack says children should have a basic structural screening by a podiatrist. “Doing so would not only greatly decrease injuries but increase sports performance and later decrease arthritic changes,” notes Dr. Pack.

References

1. Schuster RO. Podiatry and the foot of the athlete. J Am Podiatr Assoc. 1972; 62(12):465-8.
2. Saxena A, Haddad J. The effect of foot orthoses on patellofemoral pain syndrome. J Am Podiatr Med Assoc. 2003; 93(4):263-71.
3. James SL, Bates BT, Osternig LR. Injuries to runners. Am J Sports Med. 1978; 6(2):40-50.
4. Jernick S, Heiflitz NM. An investigation into the relationship of foot pronation to patellofemoral pain syndrome. In Rinaldi RR, Sabia ML (eds.) Sports Medicine ‘79. Futura Publishing Company, Mt. Kisco, New York, 1979, pp. 1-31.
5. Eng JJ, Pierrynowki MR. The treatment of patellofemoral pain syndrome. Phys Ther. 1993; 73(2):62-68.
6. Emami MJ, Glaahramani MH, Abdinejad F, Namazi H. The Q angle: an invaluable parameter for the evaluation of anterior knee pain. Arch Iran Med. 2007; 10(1):24-26.

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Author(s): 
Guest Clinical Editor: Joseph C. D’Amico, DPM, DABPO

These expert panelists share their approach to limb length discrepancies and the roles that orthotics and orthotic modifications can play in addressing these discrepancies. They also offer pearls on conservative care for Morton’s syndrome.

Q:

What method do you use for assessing limb length discrepancy and how do you determine if the degree of discrepancy is contributing to the presenting pathology?

A:

As Joseph D’Amico, DPM, notes, most experts and texts indicate that a limb length discrepancy of 1 to 1.5 cm is extremely common and does not produce pathological effects in the average individual. However, he says almost everyone agrees that discrepancies greater than 1.5 cm and certainly those over 2.0 cm produce pathomechanical consequences and symptomatology.

   “Determining the importance, degree of abnormality and correction for leg length discrepancies remains one of the most controversial issues in medicine today,” notes Lou Pack, DPM.

   Acknowledging how comprehensive the subject of limb length discrepancy is, Dr. Pack says physicians often focus on the best method of measuring length differences but emphasizes it is more important to focus first on whether those differences are structural or functional.

   “If we don’t, those measurements, as accurate as they may be, may at times be worthless,” says Dr. Pack.

   J. David Skliar, DPM, cautions that limb length discrepancy measurement is only meaningful when the patient is standing with equal weight on both limbs (if possible) in an anatomical stance position. Both he and Dr. D’Amico suggest palpating the anterior superior iliac spine or posterior superior iliac spine, and then have the patient place his or her thumbs in the same position, which can help achieve a more accurate visual impression of which side is elevated.

   One should place index cards under the short limb’s heel in increasing numbers until the pelvis appears level. At this point, Dr. Skliar says one should remove the index cards and measure the thickness of the cards with a standard ruler.

   Similarly, Dr. Skliar advises that the simplest way of determining if the limb length discrepancy is related to presenting pathology is to place a temporary lift of at least half the measured shortening to the patient’s shoe. If there is considerable pronation to the same foot, he says one should use an inversion strapping with the heel lift.

   Furthermore, the limb length discrepancy should correlate with a clinical examination of the subject’s gait, according to Dr. Skliar. He notes that if the center of gravity shifts to the short side, the longer limb may be externally rotated or the corresponding foot may be pronated with or without genu valgum. The shoulder of the longer limb is usually lower, yielding what he notes would appear to be a longer arm length.

   Dr. D’Amico assesses limb length via computer assisted gait analysis two weeks after dispensing the orthotic. He says parameters that are particularly important to be symmetrical include: calcaneal stance duration, single limb support, stance, swing, midstance and propulsive phases of gait.

   In his biomechanical examination, Dr. D’Amico notes the position and symmetry of the limbs first while the patient is seated. Then with the patient standing, he places his hands on the superior brim of the pelvis and notes any asymmetry. In this manner, one can easily observe discrepancies of less than ½ inch, according to Dr. D’Amico.

   Dr. D’Amico and Dr. Skliar recall seeing Richard O. Schuster, DPM, place a large carpenter’s level across the patient’s knees while he or she was seated to assess below knee shortages and then recheck it with the patient in neutral subtalar position.

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